Accelerating sodium polymerizations



Jan. 24, 1956 A. H. GLEAsON ETAL ACCELERATING SODIUM POLYMERIZATIONSFiled Oct. l5. 1952 .5525@ zoEB mr .5015 mme MEE/.K

,n o t n w. o. n 3 oN n om m m ovm #o S l ma N oww m S. n Q cw om o9Joseph F. nels on .B16 (Ulm-T1216 United States Paten'tO ACCELERATINGSODIUM POLYMERIZTIONS Anthony H. Gleasonywestfield, andJosephlF.""Nelsou,

Rahway, N. J., assignors'to 4Esso-rResearch-'and Enginearing Company, acorporation olwDelaware This invention relates to hydrocarbonpolymerization reactions in which sodium is used as the catalyst andmore particularly relates to means for acceleratingzthe later stages ofsuch reactionsI when the reaction has slowed down or even stopped.

The use of sodium as the catalyst for the polymerization of variousunsaturated-hydrocarbons .is well known. It is particularly useful as acatalyst inthe polymerization of butadiene and the copolymerization ofbutadiene and styrene to form rubbery copolymers. Recentlyv it has founduse as the catalyst for the preparation of synthetic drying oils by thecopolymerization of -butadiene and styrene under certain specificconditions.

In all of these reactions it sometimes happensfthat the reaction doesnot proceed at a reasonably .uniform rate. Thus an initial rate of l to20% conversion Vper hour during the first half of the polymerizationmaybe followed by rates as low as 1 to 5% in the laterA stages.. Infact, the reaction may even-stop altogether at some intermediate level.The exact reason for such .behavior is not known, but it appears that itmay be due to certain slowacting poisons which may be present `in themonomers or the diluent. Attempts to revive polymerizations which havebeen prematurely terminatedl or'retarded by the addition of fresh sodiumhave not been successful withinpractical time limits because of the factthat ysodium is relatively slow acting at temperatures -usedin.the'polymerizations even with pretreated diolens. Y

According to the present invention, .it has beenV found that theaddition of small amounts of metallic .potassium to reactions which haveslowed down or stopped produces an immediate response. A break isValways produced in the rate curve beyond which the slope islconsiderably greater. This controllable improvement in reaction rate isa definitely surprising result since the presence of potassium in theinitial catalyst to reduce the induction period leads to undesirablerunaway reactions. occur when potassium is added in the late .stagesofthe reaction.

While the present invention is suitable Afor all types of polymerizationinvolving the use of sodium as the catalyst,

it is particularly suitedto^-the preparation .ofsyntheticdrying oils 4bythe copolymerization of butadiene and styrene, inaccordance 'with theprocess described inSerial No. 176,771, filed 'July 29,V` 1950, in thename of Anthony H. Gleason.

In accordance with the disclosure in the above mentioned application, 75to 85 parts of butadiene are copolymerized with 25 to 15 parts ofstyrene in the presence of metallic sodium.

The polymerization is carried out in a reaction diluent at temperaturesranging from about 25 C. to 95 C., temperatures between 40 C. and 90 C.are particularly preferred. As a polymerization catalyst about 1.2 to 5parts, preferably 1.2 to 3 parts, of finely divided sodium per 100 partsof monomers, is used. In the case of continuous polymerizations, higheramounts of sodium are desirable.

This does not parts of monomers.

. -propanol to the polymerized charge.

1 2,732,412 Patented Jan. 24, 1956 (boiling lrange about C. to 120 C.)or straight run mineral spirits such as Varsol (boiling range about C.to 200 C.), but butane,pentane, benzene, toluene, xylene, cyclohexane orsimilar inert hydrocarbons are also useful, individually or in admixturewith each other. In general, the aromatic solvents are not so desirableas the aliphatic ones because of the toxicity of the former. Thehydrocarbon .diluents are used in amounts ranging from 50-to 500,preferably 100 to 400 parts per 100 parts of monomers.

Furthermore, to promote the reaction and to assure the formation of aproduct of proper clarity, viscosity and drying rate, itisalsopdesirable to employ in the polymerization about 1 to 100 parts ofan ether promoter'per 100 Cyclicdiethers of 4 to 8 carbon atoms nothaving an -O-C-O- group in a cylic structure, such as dioxane-1,4 andits methyl and ethyl homologues, have been found as particularlyeffective promoters. Other suitable ether promoters are aliphatic monoordi-ethers of 4 to 8 carbon atoms, such as diethyl ether, diethyl etherof ethylene glycol, and diethyl ether of diethylene glycol. Finally, itis also beneficial in many cases, although not essential, to use about 5to 35 weight per cent (based on sodium) of an alcohol such as methanol,isopropanol or n-amyl alcohol, especially where the sodium catalystparticles are relatively coarse.

The following rrecipe will illustrate the preparation of the drying oil:80 parts of butadiene-1,3, 20 parts of styrene, 200 parts of straightrun mineral spirits boiling between 150 and 200 C., 40 `parts ofdioxane, 0.2 parts of isopropanol and 1.5 parts of finely dispersedsodium are heated .at about 50 C. ina closed reactor provided with anagitator. Complete conversion is obtained in about 4.5 hours when thereaction proceeds satisfactorily, whereupon the catalyst is destroyedbyladding an excess of iso- The crude product is cooled, neutralized withcarbon dioxide or glacial acetic acid` or other anhydrous organic acidand filtered. Insteadof destroying the unreacted sodium with alcohol,the acid maybe added directly to the crude product. A

`slight excess of acid is used in order to quickly destroy the sodium.After adding ammonia to reactwith excess acid, the product is filtered..The filtrate is then fractionally distilled to remove the alcohol,modifiers suchas dioxane, and the-hydrocarbon solvent to the extentdesired. A polymeric product containing about 50-l00% non-volatilematter is obtained, the .non-volatile matter being a drying oil havingan intrinsic viscosity of 0.04 to 0.3 depending on the .reactionconditions. The most desirable viscosity range for the drying oil is0.05 to 0.22 intrinsic viscosity, which corresponds to 0.2 to 3 poisefor a 50 wt. percent solution of the drying oil in Varsol, a mineralspirit having a boiling range of 15G-200 C.

The advantages of the invention will be better understood from aconsideration of the following experimental data which are given for thesake of illustration, but without intention of limiting the inventionthereto.

Example 1 Eighty parts of butadiene of 98.5% purity and 20 parts ofstyrene were copolymerzed in 200 parts of Varsol, 30 parts of dioxeneand in the presence of 1.5 parts of finely dispersed metallic sodium and0.3 part of isopropyl In another run employing the same conditions as inExample 1, the reaction stopped unaccountably at 50% conversion. Theaddition of 0.1 to 0.2 part of potassium reactivated the reaction toeect a normal completion of the run.

Example 3 In a third run employing similar conditions as in thepreceding examples except that 1.7% sodium based on monomers was used,0.2% potassium based on monomers was added after 43% conversion. Thiswas compared to a run made under the same conditions except no potassiumwas added at any point. In both cases the reaction was carried to 100%conversion. The addition of the potassium, as shown in the attachedchart, resulted in a marked acceleration of the reaction rate ascompared to the reaction carried out in the absence of potassium. Aconversion of 100% was reached after 5.5 hrs. when the potassium wasadded as compared to 8% hrs. when no potassium was added.

The above examples clearly show the beneficial eiect of adding potassiumto a sodium-polymerized diolefin reaction which has materially sloweddown or stopped. The addition of the potassium is not restricted to anyparticular range of conversion levels and is only limited by practicalconsideration such as the vigor of the ensuing reaction. Under theconditions of Example 1, the potassium may suitably be added atconversion levels of 40 to 85 or 90%, depending on the prevailing rateof polymerization and the degree of acceleration desired. The amount ofpotassium which must be added is relatively small and varies between 0.1and 1.5 wt. percent based on monomers. The potassium cannot be added inthe initial 4l .u 2. In a process for copolymerizing a mixture of 80partsby weight of'butadiene and 2O parts by weight of stages of thepolymerization since uncontrollable high reaction rates ensue.

The nature of the present invention having been thus fully set forth andspecic examples of the same given, what is claimed as new and useful anddesired to be secured by Letters Patent is:

l. In a process for copolymerizing a mixture from 75 to 85 per cent ofbutadiene and 25 to 15 per cent of styrene in to 500 parts by weight ofa hydrocarbon diluent, per 100 parts of monomers and 1 to 100 parts byweight of a member of the group consisting of aliphatic ethers of 4 to 8carbon atoms, dioxane-1,4 and the methyl and ethyl derivatives ofdioxane-1,4 in the presence of 1.2 to 8 parts by weight of linelydivided sodium at a temperature between 40 and 95 C. in which thereaction has slowed down or completely stopped prior to the completionof the reaction, the improvement which comprises adding 0.1 to 1.5weight per cent of finely divided potassium, based on monomers, at thepoint at which the reaction slows down or stops whereby the reaction isreactivated.

styrene in 200 parts of hydrocarbon diluent, 1.5 to 1.7 parts by weightof linely divided metallic sodium, 30 parts by weight of dioxanel,4, 0.3part by weight of isopropyl alcohol at 50 C. in which the reaction hasslowed down or completely stopped prior to completion of the reaction,the improvement of which comprises adding 0.1 to 1.5 weight per cent oftinely divided potassium, based on monomers, at the point at which thereaction slows down or stops whereby the reaction is reactivated.

3. In a process for copolymerizing a mixture of parts by weight ofbutadiene and 2O parts by weight of styrene in 200 parts of hydrocarbondiluent, 1.5 to 1.7 parts by weight of finely divided metallic sodium,30 parts by weight of diethyl ether, 0.3 parts by Weight of isopropylalcohol at 50 C. in which the reaction has slowed down or completelystopped prior to completion of the reaction, the improvement of whichcomprises adding 0.1 to 1.5 weight per cent of iinely divided potassium,based on monomers, at the point at which the reaction slows down orstops whereby the reaction is reactivated.

4. In a process for polymerizing a conjugated dioletin in 50 to 500parts by weight of a hydrocarbon diluent per parts of monomers and inthe presence of 1.2 to 8 parts by weight of linely divided sodium as thecatalyst at a temperature between 40 and 95 C. and in which the reactionhas slowed down or completely stopped prior to the completion of thereaction, the improvement which comprises adding 0.1 to 1.5 weight percent of finely divided potassium based on monomers at the point at whichthe reaction slows down or stops whereby the reaction is reactivated.

5. Process according to claim 4 in which the conjugated diolein isbutadiene-1,3.

6. Process according to claim 5 in which the polymerization is carriedout in the additional presence of 1 to 100 parts by weight of a memberof the group consisting of aliphatic ethers of 4 to 8 carbon atoms,dioxane-1,4, and the methyl and ethyl derivatives of dioxane-l,4.

7. Process according to claim 5 in which the reaction is carried out inthe additional presence of 0.3 part by weight of isopropyl alcohol.

8. In a process for copolymerizing a mixture of from 75 to 85 per centof butadiene and 25 to 15 per cent of styrene in 50 to 500 parts byweight of a hydrocarbon diluent per 100 parts of monomers and in thepresence of 1.2 to 8 parts by weight of finely divided sodium as thecatalyst at a temperature between 40 and 95 C. and in which the reactionhas slowed down or completely stopped prior to the completion of thereaction, the improvement which comprises adding 0.1 to 1.5 weight percent of finely divided potassium based on monomers at the point at whichthe reaction slows down or stops whereby the reaction is reactivated.

9. Process according to claim 8 in which the reaction is carried out inthe additional presence of 0.3 weight per cent of isopropyl alcohol.

References Cited inthe file of this patent Marvel et al.: Journal ofPolymer Science, vol. 1 (April 1946), pages 275-288 (14 pages).

1. IN A PROCESS FOR COPOLYMERIZING A MIXTURE FROM 75 TO 85 PER CENT OFBUTADIENE AND 25 TO 15 PER CENT OF STYRENE IN 50 TO 500 PARTS BY WEIGHTOF A HYDROCARBON DILUENT, PER 100 PARTS OF MONOMERS AND 1 TO 100 PARTSBY WEIGHT OF A MEMBER OF THE GROUP CONSISTING OF ALIPHATIC ETHERS OF 4TO 8 CARBON ATOMS, DIOXANE-1, 4 AND THE METHYL AND ETHYL DERIVATIVES OFDIOXANE-1, 4 IN THE PRESENCE OF 1.2 TO 8 PARTS BY WEIGHT OF FINELYDIVIDED SOLDIUM AT A TEMPERATURE BETWEEN 40 AND 95* C. IN WHICH THEREACTION HAS SLOWED DOWN OR COMPLETELY STOPPED PRIOR TO THE COMPLETIONOF THE REACTION, THE IMPROVEMENT WHICH COMPRISES ADDING 0.1 TO 1.5WEIGHT PER CENT OF FINELY DIVIDED POTASSIUM, BASED ON MONOMERS, AT THEPOINT AT WHICH THE REACTION SLOWS DOWN OR STOPS WHEREBY THE REACTION ISREACTIVATED.